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IB DP ESS — Topic 3: Biodiversity and Conservation (HL Extension) | HL | Paper 1 & Paper 2A/2B
🎯 Learning Intentions By the end of this note, you will be able to:
- Define artificial selection, selective breeding, and genetic modification, distinguishing between natural and human-directed evolutionary processes.
- Explain how human activities accelerate evolutionary change in wild populations, including antibiotic resistance, pesticide resistance, and trophy hunting-driven selection.
- Describe the geological and fossil record as evidence for past biodiversity and mass extinction events, and how the current biodiversity crisis compares to these historical baselines.
- Analyse the concept of the Anthropocene as a proposed geological epoch, evaluating the stratigraphic evidence for human impact on Earth systems.
- Evaluate the ethical, ecological, and evolutionary implications of de-extinction technologies and genetic engineering in conservation contexts.
- Discuss contrasting worldviews — ecocentric, technocentric, and anthropocentric — in relation to human manipulation of evolutionary processes and Earth history.
- Justify why understanding evolutionary timescales and Earth history is essential for contextualising the current biodiversity crisis and designing effective conservation strategies.
Real-World Context & Relevance
In 2019, researchers studying bighorn sheep in Alberta, Canada, published a striking finding: decades of trophy hunting — targeting the largest-horned males — had driven a measurable evolutionary shift in the population. Average horn size had declined by approximately 20% over 30 years, a change far too rapid to be explained by genetic drift alone. The hunters, by consistently removing the most reproductively successful males before they could pass on their genes, had effectively become a selective pressure acting on the population. This is evolution in real time, driven not by natural predation or climate but by human preference and economic incentive.
This example is not an isolated curiosity. Across the globe, human activities — from antibiotic overuse in hospitals to pesticide application in agriculture, from selective fishing to urban heat islands — are reshaping the evolutionary trajectories of thousands of species simultaneously. At the same time, the geological record shows us that Earth has experienced five previous mass extinction events, each reshaping the biosphere over millions of years. The current rate of species loss — estimated at 100 to 1,000 times the background extinction rate by the IPBES Global Assessment (2019) — suggests we may be initiating a sixth, but at a pace that leaves evolutionary adaptation little time to respond.
🌍 Why This Matters Human activities are now a primary driver of evolutionary change across the biosphere, operating at timescales orders of magnitude faster than natural selection. Understanding how we alter evolutionary processes — and how the fossil record contextualises current biodiversity loss — is essential for designing conservation strategies that work with, rather than against, the logic of life on Earth.
Core Concepts & Definitions
To understand how humans alter evolution, we must first appreciate what evolution actually requires: heritable variation within a population, differential reproductive success linked to that variation, and sufficient time for allele frequencies to shift. Natural selection operates across geological timescales — but human pressures can compress this process dramatically, producing observable evolutionary change within decades or even years.
📖 Key Definition — Artificial Selection (Selective Breeding) Artificial selection is the process by which humans intentionally breed organisms with desired heritable traits, thereby directing evolutionary change in domesticated species. Unlike natural selection, the selective pressure is determined by human preference rather than environmental fitness.
Artificial selection has been practised for at least 10,000 years, since the domestication of wolves into dogs and wild grasses into cereal